It was clear already in the first teaser for Kingdom Hearts IV that the graphic detail level has been raised, and they also use Unreal Engine 5 (although the trailer was rendered in an earlier version of the graphics engine) to achieve this increased level of detail.
But the graphics are actually important for the game’s content, this is because the team behind the game focuses on creating deeper and more visually detailed worlds, which means that there will apparently not be as many. In an interview with Game Informer says director Tetsuya Nomura like this about the new priorities:
“As far as the graphic qualities … since with each new title, the specs have been really increasing and there’s so much more we can do in terms of graphics, it kind of limits the number of worlds that we can create in a sense . At this time we’re considering how to approach that, but there will be Disney worlds in Kingdom Hearts 4. “
It is not yet known which worlds we will visit.